Percutaneous access to the cardiovascular system is used to diagnose, evaluate, and treat a variety of conditions. A typical procedure involves passing a wire guide through an opening in a patient's skin to a vascular structure such as a vein or artery. The wire guide can then be passed through the cardiovascular system to a location of interest within the patient. Once the wire guide has been appropriately positioned, a catheter may be guided by the wire guide to a location where a procedure is to be performed. Angioplasty, imaging, and the placement of stents, grafts, filters and other devices, are common procedures which are performed according to variations of the above general technique. It is also common to use percutaneous access for the placement of catheters which deliver fluid at an intraluminal treatment site. Devices known as infusion catheters are commonly used to deliver a therapeutic treatment fluid such as a thrombolytic agent to a clot or other undesired tissue within a vein or artery. A wide variety of infusion catheter designs are known and commercially available. One general class of infusion catheters utilizes a longitudinally extending lumen which connects a supply of therapeutic fluid located outside of the patient with an intraluminal space by way of ports communicating between the lumen and the intraluminal space.
A typical infusion procedure involves leaving an infusion catheter within a patient for a period of time while treatment fluid flows from the fluid supply into the infusion catheter, and thenceforth into the intraluminal space. A variety of factors can influence how long the infusion procedure lasts. The size of the vascular structure which includes the treatment site, the type of treatment fluid such as a type of lytic agent, geometry and/or age of a clot or other intravascular material, and still other factors such as the distance fluid must travel from the fluid supply to the treatment site, can all affect the selection and administration of a particular infusion procedure. Decisions regarding the selection and administration of a particular infusion procedure are generally made by the attending clinician, and may be updated as the procedure progresses. In any event, there can be a relatively wide range in infusion procedure duration, volume of fluid infused, infusion technique such as pulsed or continuous flow and the particular type of infusion catheter used. In some instances fluid may be infused, often at a relatively high infusion pressure, for a relatively short period of time, for example less than one hour. In other cases, the total infusion time may be five, six or even twelve hours or greater, and infusion may take place intermittently or more or less continuously at a range of different infusion pressures, from relatively low to relatively high.
While various practices have been successful for years, there remains room for improvement. Basic assumptions exist about the operation and behavior of infusion catheters while resident in a vein or artery. For example, it is often assumed that all portions of an infusion length of an infusion catheter will predictably, reliably and uniformly infuse fluid into an intraluminal treatment site throughout the entire course of an infusion procedure. These basic assumptions may not always be valid, however, particularly for procedures using relatively low infusion pressures and prolonged residency of an infusion catheter in a vein or artery.